One example of a cutting tool which is rotatable about a central axis such as a drill or an end mill is the drill disclosed in Japanese Patent Laid-Open No. Hei 4-275812 (Patent Literature 1). As disclosed in Patent Literature 1, a cobalt-containing cemented carbide alloy is generally used as the base material of the drill. In addition, a diamond layer may be formed on the surface of the drill in order to improve the wear resistance of the cutting edge of the drill.
In a case where the cobalt content of the cemented carbide alloy is high, a layer made of graphite instead of diamond is easily formed at the formation of the diamond layer. This is because, when coating a member made of a cemented carbide alloy with diamond, graphite rather than diamond tends to be preferentially generated on the cobalt. Therefore, there is a demand for the cobalt content of the cemented carbide alloy used as the drill material to be low in order to satisfactorily carry out the diamond coating. However, when the cobalt content is excessively low throughout the cemented carbide alloy to be used, there is a problem in that the strength of the drill is reduced.
The present invention has been made in consideration of the problem described above, and an object of the present invention is to provide a cutting tool favorably coated with diamond while obtaining a favorable strength using a cemented carbide alloy.